The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Recently, there have been demands for technologies such as detecting and warning a passenger, a companion animal, and/or the like if the passenger, the companion animal, and/or the like remains in a rear seat.
Thus, a system of having a radar sensor or the like around a room lamp in a vehicle and detecting a passenger and/or a companion animal which remains in a rear seat has been developed.
However, due to properties of the radar sensor, an iron product may be detected, but there may be a shadow region where an object which remains in a rear seat is not detected by a headrest, a seat frame, and the like if a driver or a passenger alights from a vehicle in a state where a driver seat or a passenger seat is inclined backward.
Particularly, if an infant, a companion animal, or the like with a small body is located in the shadow region, it may be difficult to detect them through the radar sensor.